The invention resides in a method operating a particle filter in an exhaust system of a motor vehicle's internal combustion engine which particle filter is subjected to repeated soot burn-off procedures.
DE 101 54 261 A1 discloses a method for determining the charge of a particle filter. In that method, particle filters as they are used in the exhaust systems particularly of motor vehicle Diesel engines for filtering soot particles out of the exhaust gas, are considered. On or in the particle filters, the retained soot particles slowly accumulate which results in an increasing charge of the filter and a slow increase of the flow resistance of the particle filter. As a result, the exhaust gas backpressure of the filter is increased by the collected particles, which detrimentally affects engine operation. By burning off the collected soot particles, the soot charge of the particle filter can be reduced and a low flow resistance of the filter can be re-established.
The particle filter charge however also includes a collection of ash which cannot be removed by the soot burn-off procedure since the ash consists of non-burnable inorganic substances. The method described in DE 101 54 261 A1 makes it possible, to distinguish between the charge of ashes collected in the particle filter and the charge of soot particles collected in the filter by a determination of the pressure loss across the particle filter. The method makes it therefore possible to determine the success of a soot burn-off procedure. A slow increase of the flow resistance because of an increasing ash charge however cannot be prevented by that procedure, and, finally will lead to uselessness of the particle filter.
Since generally, it is assumed that the ash charge of the particle filter cannot be reduced during operation of the vehicle and particularly not by the common soot burn-off procedure, DE 41 34 949 D1 proposes that the ashes collected in the particle filter are blown out of the filter in a direction opposite to the normal exhaust gas flow direction when the vehicle is present in a service facility. In this way, an inadmissibly high flow resistance of the particle filter can be reversed and the particle filter is then available for further use. However, this method is relatively complex and requires an interruption of the operation of the vehicle.
It is therefore the object of the present invention to provide a method for the operation of a particle filter of a motor vehicle engine whereby the ash charge of the particle filter can be reduced during operation of the motor vehicle.